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Technology Goes Deep on Land and Subsea

You would have to go 5000–6000' (1524–1829 m) under water to see the AZ-10 fully concentric vertical mono-bore subsea tree operating in its natural working habitat. The AZ-10 subsea tree manufactured by Argus Subsea (Houston) is off-the-shelf hardware that can operate effectively anywhere a rig can power a blowout preventer (BOP). The AZ-10 features a standard horizontal tree design with a universal tubing hanger system that runs in any 18.75" (476 mm), 10,000 or 15,000 psi (69 or 103 MPa) wellhead. With a concentric design for all downhole and tubing hanger-to-tree interfaces, it can be quickly and cost effectively put into service.

The AZ-10 subsea tree illustrates the precision machining challenges that oil field accessories and their components present. The unit weighs in at about 50,000 lb (22,680 kg), is light enough to be handled safely with rig cranes, and is easily transported to the moon pool for deployment. The AZ-10 requires only five running tools versus 20–30 typically found on comparable subsea tree systems and is designed for 20 years of service life in production, injection, or well test operations.

The hanger system on the AZ-10 operates on a lock-and-seal system that uses mechanical and hydraulic sealing within the tubing hanger. A key component designed into the AZ-10 is the AMLOK hydraulic rod lock provided by Advanced Machine & Engineering (AME; Rockford, IL). To address the issues of depth and pressure, AME engineered the rod locks from 4140 steel with electroless nickel plating and a specially formulated two-part epoxy to create a completely sealed unit. Marine grade lubricant was used.

With the external sealing system of the AZ-10 and the wide variety of connections involved, the construction of the rod lock also needed to accommodate the unique challenges of force over distance in a wide window of installation conditions. Since the customer’s requirement was very cost sensitive, it was necessary for AME to create a one-size-works-for-all unit, an application engineering challenge that AME engineers were able to meet.

When Counting Rigs Add Multiple Horizontal Shafts

With current oil prices hovering just under $100 a barrel for West Texas Intermediate and natural gas prices at $4.25 per thousand cubic feet (vs. a not-breaking-even disincentive of $3–$3.25 per thousand cubic feet), the year ahead looks to be good based on OEM activity, especially subsea. With the continuing success of fracking in North America, it’s likely that major OEMs will continue to redeploy assets from overseas plays for investment into the newly profitable US shelf plays. The impact on machine tool builders and suppliers of everything from the latest machining centers, CNC lathes, boring mills, and ancillary equipment will continue to drive developments in their latest technology offerings.

Rig counts, which are closely watched to gage oil & gas industry activity, have taken on new meaning. In the past, one rig typically meant one well. Today’s rig-count math is based in part on the latest technology of horizontal drilling, which multiplies the number of possible wells attached to each rig. One well may have three to five different horizontal shafts going off it. Since midyear 2013, for example, North American rig count, which includes all land-based rigs and subsea in the Gulf of Mexico, has pretty much remained on the low end of the 1700 and 1800 range. At the end of November, for example, 1709 rigs in operation would equate to over 9000 wells at about 5.4 wells per rig. Though the lion’s share of domestic rigs in Texas and the Southwest are single vertical shaft, converting these vertical shaft wells over to horizontal drilling dramatically impacts and increases the amount of accessories including mud pumps, liner casing, cementing tools, packers and mandrels and fracking tools, accessories that remain downhole, and, of course, Christmas trees.

Special Boring Option Meets Tubular Needs

“We basically ask our customers what would they like to see on their machine tool to help them do their jobs more efficiently, and we’ll go ahead and incorporate some of their suggestions,” said Dana Scott, general manager-Houston Technology Center, Mazak Corp. (Florence, KY).

“A good example resulted from the request of an oil service OEM customer who asked for the capability to bore very deep holes in tubing. A traditional approach is to put long boring bars on the turret with other required tooling but then you encounter major tooling interference,” said Scott. Based on the customer’s request, Mazak developed a long boring-bar option mounted on the programmable tailstock for QTN450 series CNC lathes.

“It provided a cost-effective solution for deep boring tubing and casing to depths of 36" [914-mm], even in Inconel, while holding very tight tolerances and excellent surface finishes,” said Scott. “The QTN 450 with 7.2" [183-mm] spindle bore is the most popular model in the oil patch with bed lengths from 40 to 120" [1016-3048 mm]. With the long boring-bar tailstock our customers have the capability of processing deep bores in addition to the standard 12-station turret tooled for other part machined features for maximum flexibility.”

Machine tool builders like Mazak and their customers continue to benefit from close relationships with key OEM suppliers of tooling, workholding and software. “Our VIP tooling partners, for example, have developed new boring bars with different types of materials and designs that keep harmonics from developing and damaging surface finishes,” said Scott. “In the past prior to having this technology, it wasn’t uncommon for operators and programmers to strap lead weights to boring bars for dampening to minimize chatter during the boring and/or threading process of internal diameters.”

Threading Critical to Integrity of Heavy Pipe Strings

For the all-important threading of drill pipe and casing, Mazak has developed its PT20 Premium Threading System, which rotates the tool around the part instead of having to rotate pipe that is 30 or 40' (9 or 12-m) long with diameters up to 20" (508 mm) and weights over 18,000 lb (8165 kg). “There are two basic thread types in the oil patch: Premium and API threaded connections. The Premium threads are patented proprietary forms that are used where a very rigid connection and good seal surface are required, especially in deep subsea well applications. The PT20 system provides accurate cutting of these patented thread forms and seal surfaces fast and efficiently on swedged pipe or casing. By incorporating the Renishaw measuring system to probe the drill pipe’s ID and OD and adjusting for straightness, we can maintain even wall thickness. Another major benefit is changeover from one diameter size to the next is 20 minutes rather than three hours,” said Scott.

Emuge Corp. (West Boylston, MA) has introduced an extensive and expanded thread milling program, which includes a new line of solid carbide thread mills and insert thread milling systems for oil and gas manufacturing applications. “The oil & gas industry requires highly secure, predictable machining processes for accurate threads in demanding materials such as chrome-moly steels, stainless and nickel alloys,” said Mark Hatch, Emuge product director, taps and thread mills. “Our new oil and gas thread milling program exceeds these requirements with high feed rates, innovative features and more cutting edges for today’s complex parts such as blowout preventers, valves, frack pumps and other energy-related parts.”

Machines Match Energy Machining Needs

“DMG Mori has a fully developed portfolio of large machines, which can handle the large and long parts and tubes that are required in oil & gas industry machining,” said Nitin Chaphalkar, advanced solution development manager, DMG Mori (Hoffman Estates, IL). “Oil field customers aren’t really that different from others in the aspect that they would like to improve productivity and throughput. They produce big expensive parts that are typically heavy and difficult to handle. Productivity improvements for these customers come from producing first-part good-parts in a minimum number of setups and, above all, reducing scrap. Another important facet of the oil & gas industry is the need for machining replacement parts in much smaller volumes,” said Chaphalkar.

“We are working on some special machining processes for machining specific features for machining long tubular parts. For machining the insides of tubes, for example, you need a long boring bar option. The NT 6600 is a 6-m X-axis machine with a 600-mm chuck size that is well-suited for these applications. Also, the NLX is designed for heavy-duty machining of difficult-to-machine hard metals like stainless and Inconel,” said Chaphalkar. The NLX 4000 is a rigid four-axis lathe with two turrets that can be used for performing a variety of processes on large tubes. The NLX is equipped with a tailstock and a big bore spindle for long tubes to be passed through.

“For large diameter parts, the DMU series of machines up to the DMU 600P with a 6-m X-axis stroke can handle a part with a 4 to 5-m diameter. It’s available in sizes with 2.4-m X axis and 2.7-m X axis. These machines are very flexible and can do turning where needed. Our latest development is making gears on our machines for oil field and energy applications where the parts are long and the setup time is high. The more operations you can combine on a single setup, the more part handling is reduced and cost savings are improved. The NT series machines and various DMU models, all can cut various types of gears, including everything from helical, spur, herring bone, to bevel gears,” said Chaphalkar.

Machines Built for Challenging Conditions

“Machine tool rigidity, versatility, and accuracy are among the most critical considerations in the manufacture of oil & gas components,” said Dale Hedberg, Feeler product manager, Methods Machine Tools Inc. (Sudbury, MA). “Machine tools must be exceptionally strong and rigid to be capable of accurately producing large, heavy-duty parts comprised of exotic materials. At the same time, machines should be versatile to perform complex machining required to produce many oil & gas components. Challenging conditions put extreme demands on equipment, for example, drillheads that might need to go down two to three miles require high accuracy in order to prevent any failure.”

“Machines that are well-suited for the manufacture of oil & gas components from Methods Machine Tools include the Feeler double-column bridge-style machines that offer the rigidity and strength required to accurately manufacture large, cumbersome components. The machines also feature a stepped Y-axis beam and weigh up to 82 t, contributing significantly to rigidity. For extra machining power, the Feeler bridge machine’s German ZF gearbox design provides optimal spindle performance and a 4-to-1 gear ratio, for maximum power and torque at lower rpm,” said Hedberg.

The Feeler FV-Series bridge mills facilitate the production of large high-quality components with THK linear guideways on the X axis, and Schneeberger roller linear guideways on the Y axis. X-axis travels range from 85 to 284" (2160–7200 mm) and Y-axis travels range from 55 to 158" (1400–4000 mm). The Z axis features boxway construction and travel of 35.4" (900 mm) with an optional 47.2" (1200-mm) travel available. Feeler boring mills feature ultra-high precision for machining large workpieces and four-axis capability for work on multiple part surfaces. In addition, these systems offer a large, 5" (127-mm) quill diameter with 27.5" (698 mm) of travel and linear scales in X, Y and Z axes for precise machining of large components.

Multifunction Machines Fit Various Strategies

“Okuma offers a number of multifunction machines for producing downhole components, some of which [LOC series] are capable of simultaneous four-axis cutting with balanced loads on both turrets,” said Tim Caron, Houston Tech Center Coordinator, Okuma America Corp. (Charlotte, NC). “The Multus series general-purpose multifunction CNC lathe, for example, is available with a long bed.” When equipped with a subspindle the machines reduce setup time by virtually eliminating repetitive fixturing. The Multus B750 with W spindle hands the part from one spindle to the other to complete milling and turning operations without changing the part. Programming of both lathe and machining center processes are handled by the Okuma THINC OSP control with advanced functions like its exclusive Collision Avoidance System software for achieving high accuracy.

Multus U series are the newest additions to the Okuma lineup of multifunction machines. The Multus U3000 and U4000 provide rigid and thermally stable platforms for turning, milling, through holes, deep drilling contouring, threading and other operations. Optional opposing (W) spindles and an optional lower turret provide flexibility for a wide variety of configurations and parts. The 240° swing on the B axis provides full machining areas for both the main and subspindles. The 22-kW output of the U3000’s two-step gear develops a maximum torque of 427 N•m while the speed climbs to 5000 rpm. Y-axis travel up to 9.84" (250 mm) and Z-axis travel up to 63" (1.6 m) in the 1500 version are possible. The Multus U4000 features a 22-kW output of the two-step gear and develops a maximum torque 700 N•m, Y-axis travel up to 11.81" (300 mm) and Z-axis travel up to 82.6" (2.1 m) in the 2000 version are possible. ME

This article was first published in the February 2014 edition of Manufacturing Engineering magazine. Click here for PDF.